BIO 100 Exam 1 Study Guide: Scientific Investigation, Chemistry of Life, and Biological Macromolecules

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Scientific Investigation

The Scientific Method and Experimental Design

Scientific investigation is a systematic approach to answering questions about the natural world. It involves forming hypotheses, designing experiments, and analyzing results to draw conclusions.

Scientific Question: A testable inquiry, such as "How does light exposure affect the growth height of bean plants?"
Hypothesis: A proposed explanation or prediction, e.g., "Bean plants exposed to natural sunlight will grow taller than those under artificial or minimal light."
Independent Variable: The factor intentionally changed by the experimenter (e.g., type of light exposure).
Dependent Variable: The measured outcome (e.g., average height of bean plants in centimeters).
Control Group: The group kept under standard conditions (e.g., standard classroom lighting) for comparison.
Treatment Groups: Groups exposed to different conditions (e.g., sunlight, artificial light, bench cabinet).
Type of Investigation: Experimental, as variables are manipulated and other factors are kept constant.
Results Evaluation: Data analysis to determine if the hypothesis is supported (e.g., sunlight group grew tallest).

Example: In a plant growth experiment, the control group receives standard classroom light, while treatment groups receive sunlight, artificial light, or minimal light. The average plant height is measured to assess the effect of light type.

The Chemistry of Life

Atoms, Ions, and Molecules

All matter is composed of atoms, which combine to form molecules. Understanding atomic structure is fundamental to biology.

Atomic Number: The number of protons in an atom's nucleus (defines the element).
Atomic Mass Number: The total number of protons and neutrons in the nucleus.
Subatomic Particles:
- Proton: Positively charged particle in the nucleus.
- Neutron: Neutral particle in the nucleus.
- Electron: Negatively charged particle orbiting the nucleus.
Ions: Atoms that have gained or lost electrons, resulting in a charge.
- Positive Ion (Cation): Atom that has lost electrons (e.g., Na+).
- Negative Ion (Anion): Atom that has gained electrons (e.g., Cl-).

Chemical Bonds

Atoms combine through chemical bonds to form molecules essential for life.

Ionic Bond: Formed when one atom completely transfers an electron to another atom, resulting in oppositely charged ions that attract each other.
Covalent Bond: Formed when two atoms share one or more pairs of electrons, creating a stable molecule.
Hydrogen Bond: A weak attraction between a partially positive hydrogen atom and a partially negative atom (often oxygen or nitrogen) in another molecule.

Example: In table salt (NaCl), sodium donates an electron to chlorine, forming Na+ and Cl- ions held together by an ionic bond. In water (H2O), oxygen and hydrogen share electrons via polar covalent bonds, and separate water molecules are attracted by hydrogen bonds.

Acids, Bases, and the pH Scale

Understanding pH

The pH scale measures the concentration of hydrogen ions (H+) in a solution, indicating its acidity or basicity.

Acidic Solution: pH below 7; high concentration of H+ ions (e.g., stomach acid, lemons).
Neutral Solution: pH exactly 7 (e.g., pure water).
Basic Solution: pH above 7; low concentration of H+ ions (e.g., ammonia, oven cleaner).
Logarithmic pH Scale: Each unit change represents a tenfold difference in H+ concentration.

Examples:

pH 3 is 10 times more acidic than pH 4.
pH 10 is 100 times more basic than pH 8.
If Solution A has pH 5 and Solution B has pH 2, Solution B is 1,000 times more acidic.

Equation:

Biological Macromolecules

Classes and Functions

Macromolecules are large, complex molecules essential for life, each with unique structures and functions.

Macromolecule	Monomer (Building Block)	Function
Protein	Amino acid	Enzymes, structure, transport, signaling
Carbohydrate	Monosaccharide	Short-term energy storage
Lipid	Fatty acids, glycerol	Long-term energy storage, cell membranes (hydrophobic)
Nucleic Acid (DNA, RNA)	Nucleotide	Genetic information storage and transfer

Example: Proteins are polymers of amino acids linked by peptide bonds; DNA and RNA are nucleotide polymers; lipids are hydrophobic and form the core of cell membranes; carbohydrates provide quick energy.

Key Terms and Definitions

Term	Definition
Independent Variable	The variable intentionally changed or manipulated by the experimenter.
Dependent Variable	The variable measured or observed; the outcome response data.
Control Group	The experimental baseline group kept under standard conditions with no treatment applied.
Ionic Bond	A chemical bond formed via the complete transfer of electrons between atoms.
Covalent Bond	A stable chemical bond formed when two atoms share valence electrons.
Hydrogen Bond	A weak electrostatic attraction between a partially positive H atom and a partially negative atom.
Acidic Solution	A solution with a pH below 7 containing a high concentration of H+ ions.
Basic Solution	A solution with a pH above 7 containing a low concentration of H+ ions.
Logarithmic pH Scale	A scale where each whole unit change represents a 10-fold difference in H+ concentration.
Protein Monomer	Amino acids (linked together by peptide bonds to form polypeptides).

Practice Questions and Answers

What is the role of the unfertilized plants in an experiment? Control group.
Why must a scientific hypothesis be 'falsifiable'? It must be possible to prove it wrong.
What type of bond is formed when one atom completely transfers an electron to another atom? Ionic bond.
Inside a single water molecule, what type of bond holds the oxygen atom to the hydrogen atoms? Polar covalent bond.
What weak attractive force occurs between two separate water molecules? Hydrogen bond.
Identify the subatomic particle that carries a negative charge and orbits the nucleus. Electron.
If Solution A has a pH of 5 and Solution B has a pH of 2, how many times more acidic is Solution B? 1,000 times more acidic.
True or False: A substance that acts as a base will increase the concentration of free H+ ions. False (it decreases H+).
Which macromolecule class is entirely hydrophobic and forms the core of cell membranes? Lipids (phospholipids).
What is the monomer (building block) of a protein? Amino acids.

Additional info: Some explanations and examples have been expanded for clarity and completeness, following standard introductory biology textbooks.